Toilet Back Flow Preventer

I recently read through this thread:
https://terrylove.com/forums/showth...get-a-good-flush-through-a-backflow-preventer

I have also been considering the Suds n Flood backflow preventer. I know it looks amateurish, but like the original poster my toilet is a few feet below grade (a living floor).

I already have a backflow preventer on my main, but when the storm system gets over run I invariably get back up in my tub and toilet (there is Y joint to a sump that works very effectively until the sewer gets over run). I have plugged everything else so the only thing vulnerable is the toilet.

My question is: Is there another valve that can be installed in the line? I just don't want another hatch, so it would have to be cemented in and non-accessable accept via snake.

Taking the two evils- the poor flush of the suds n flood or the non-accessability of an in line preventer, which would you choose?

Please don't question my Fema Flood Zone A living- I'm just looking for plumbing opinions... Thanks!

quote; so it would have to be cemented in and non-accessable accept via snake.

There is NO SUCH THING. It would act like a "Chinese finger trap" if a snake were put through it, and the ONLY way to extract it would be to break the floor and pull it out "downstream".